"And both of these new versions of the tool use started at this water hole that we had amazing filming access at."

As she sat filming and watching the chimps, Dr Hobaiter saw this behaviour spread from individual to individual.

"Basically, if you saw it done, you learned how to do it, and if you didn't you didn't," she said.

"It was just this wonderfully clear example of social learning that no-one had in the wild before.

"We've had that in captivity, we've had indications in the wild, but this was the final little piece of the puzzle."

Chimp technology

Image copyrightLiran SamuniImage caption
Using moss seems to make a slightly more advanced drinking sponge

Image copyrightC HobaiterImage caption
As the researchers watched the animals, they saw the behaviour spread from chimp to chimp

The team of researchers from Anglia Ruskin University and the University of Neuchatel in Switzerland analysed the video to work out exactly how the new tool developed and spread.

Dr Thibaud Gruber from the University of Neuchatel explained that the fact that the new behaviours were "variants of the old, well-known sponge-making technique" suggested that chimpanzee culture changes "little by little" - building on previously acquired knowledge to improve an existing tool repertoire.

"With respect to humans, our findings strongly support the idea that the last common ancestors of chimps and humans could learn cultural behaviours from each other, in a similar way," he told BBC News.

Dr Susanne Schultz from the University of Manchester said it was not surprising that chimps used this social learning: "We know from captivity that they are more than capable," she said.

"But there are so few studies that can demonstrate its utility in the wild, and for this reason this paper is a big step forward."